High current applications like Microprocessors, Fuel cells, Electric Hybrid Vehicles, Solar Cells etc., use interleaved isolated buck derived converter. Interleaving of converters for such high current applications converters is done to achieve reduced input capacitor ripple voltages, output capacitor ripple current cancellation and reduced peak currents of output inductors. Generally, interleaving requires a higher number of transformers through which distributed magnetics can be achieved. i.e., one bulky transformer can be replaced with low power profile transformers. The performance of forward converter depends on core resetting of the main transformer. The core’s magnetizing energy is recycled by resetting it. In the absence of core reset, the current builds up at each switching cycle, saturates the core, causes reverse recovery problem in the diode and the active clamp will no longer in zero voltage state during turn on of the main switch. The transformer secondary output is used as a gating pulse for Synchronous Rectifiers. These have very low forward drop which are most suitable for high current applications. Among various used clamping methods, the transformer core is optimized effectively by Active center clamp reset approach. The proposed method results in less number of switches and clamping capacitor, and lower cost compared to conventional forward converter. Reduction in voltage stress without losing duty-cycle ratio is also achieved by means of a series-parallel connected switch structure with Self Driven Synchronous Rectifiers. The proposed center clamp converter overcomes the Maximum Duty cycle limitation of 50%. This paper mainly focuses on active center clamp forward converter and is also compared with Active Positive Negative clamping techniques.
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Jun 25, 2018
E.Shra Van + 1
Open Access